A tractor is provided with an endless belt which travels in a triangular path and a drive shaft located well below the level of the paper path. The tractor body has both an inner and outer body portion, each of which contains a journal bearing for support on the support shaft. An adjustable torsion spring...http://www.google.fr/patents/US4836431?utm_source=gb-gplus-shareBrevet US4836431 - Semi-automatic loading paper feed tractor
